public class demo6 {
    public static void main(String[] args) {
        //1 获取一个手机号码
        String phoneNumber = "13804475555";

        //2 截取手机号的前三位
        String start = phoneNumber.substring(0, 3);

        //3 截取手机号码的后四位
        String end = phoneNumber.substring(7);

        //4 拼接
        String result = start + "****" + end;
        System.out.println(result);
    }
}
